Electrical detection apparatus



. w W U v ass. mmm E Y l TN 0 f n N. s. RxcH 2,450,166l

Spt. 28, 1948.

2 Sheets-Sheet l LCS Patented Sept. 1948 ELECTRICAL DETECTION APPARATUSNicholas S. Rich, Milwaukee, Wil.

Application August 18, 1944, Serial No. 549,987

'I'his invention relates to apparatus for detecting the passage ofautomotive vehicles and has particular reference to traffic controldevices.

Heretoiore traillc control systems which in corporate means by which thepassage of vehicles is utilized to change the direction signals havebeen controlled by detectors which were either of the permanent magnetvor mechanical type,

the former being on the order of that illustrated in the patents to.J.L. Barker, N os. 2,201,145 and 2,201,146, and the latter being theconventional depressible switch closing strip extending across thepavement. l v

The present invention employs a detector' which is neither mechanicallyactuated nor magnetically actuated in the sense that its functioningdepends upon the vehicle cutting or distorting a eld of magnetic forceradiating from a. permanent magnet, but instead is responsive to themagnetic field radiating from a vehicle by virtue of the functioning ofits electrical equipment and to the magnetic held resulting from thedischarge ilow oi electrostatic energyaccumulated by the vehicle as aresult of tire friction and atmospheric friction'while the vehicle is inmotion.

It therefore follows that the primary purpose of this invention is toprovide a detection apparatus the functioning of which is initiated bythe movement of themagnetic fieldwhich surrounds an automotive vehiclepast a suitably located detector.

Inasmuch as the response of the apparatus is Claims. (Ci. 177-329) notdependent upon the cutting or distortion of a magnetic iield emanatingfrom a permanent magnet or the earth, the principal disadvantages of themagnetic detection devices heretofore employecl are obviated. l

For irstance. the device of this invention can be installed withoutregard for the earths magv netic iield as it is not affected thereby.The detector per se of the present system is also not aiected by normalvibration which in the case of the permanent magnet type of detector.was a fruitful source of trouble, the reason being that any relativemotion, no matter how slight, be-

tween the detector coil and the earth's magnetic iield "tripped" thesystem.

Another very important advantage oi' the pres;-

ent system over the permanent magnet type is that it is notobjectionably affected by the-proximity of ferrous metals and as a'consequence' the makeup of the pavement does not interfere with" theoperation of the system, hence no needexists for cutting away thereinforcing rodsv of the' .made as come wi As will be apparent from thedescription hereinaiter, the present system is capable of greateraccuracy than past detection apparatus as its sensitivity can beadjusted to-require the vehicle7 to be'closely adjacent to the detectorto initiate -the functioning thereof.

In-addition to the. foregoing there are many other reasons why thepresent invention surpasses the permanent magnet type of detector whichwill be apparent as this description proceeds;` and as to those systemsthat employ mechanical detectors. the advantages of the presentinvention are deemed obvious.

The difficulties vinherent in any permanent magnet type of detectorsystem such as that of the aforesaid Barker patents, led to complicatedcontrol systems which not only were costly to manufacturegand install,but extremely diilcult to maintain, and it is therefore another objectof this invention to provide a detection system or apparatus which issimple and inexpensive.

It is also a'n object of this invention to provide a detection system orapparatus which is so de. signed and constructed that it may be adaptedfor any particular type of service and which canl beso designed andyconstructed that when used for traiilccontrol any automotive vehicleapproaching an intersection will positively actuate the system,regardless 'of the speed at which the vehicle is traveling or the natureof the vehicle. 'Still another object of this invention is to provide avehicle detector apparatus that will reliably respond to and record thepassage oi every vehicle regardless of how closely one vehicle mayfollow another.

With the above and other objects in view .which will appear as thedescription proceeds this invention resides in the novel construction.combination and arrangement of parts substantially as hereinafterdescribed. vand more particularly detlned'by the appended claims. itbeing under stood that such changes in the precise embodiment of the jherein-disclosed invention may be thin the scopeof the claims. f "Theaccompanying drawings illustrate two complete examples oi the physicalembodiment of the invention constructed in .accordance with the bestmodes sofar devised for the practical ap pllcation of the principlesthereof, and in which: Figure lis adiagramma'ti'cplan view of a highwayintersection. illustrating one application of this invention: l

Figure 2 is a circuit diagram illustrating the heart oi' the System;

Figure 3 is a circuit diagram illustrating the application of theinvention to traffic control as shown in Figure l;

Figure 4 is a side .view of the detector per se of this inventionillustrating the manner in which 'it is mounted in the pavement;

embedded ln the pavement in a manner to be hereinafter described.

This detector is broadly -an inductance. and specifically itis asolenoldthe turns of which arc wound en a core 6 of special metalhereinafter to be more fully described. inasmuch as the system is notdependent upon the magnetic neld of a permanent magnet thecoil 5 neednot be wound with the extreme degree of care required of per- .manentmagnet, systemsof detection as the losses occasionedby hysteresis haveno efi'ect upon the operation of the present system.

One end of the coil 5 is connected to one side of a power condenser 1which may be either theV paper type or Ithe electrolytic type. thelatter being preferable, The other side of the power con- 'denser isgrounded and the other end ofthe coil is also grounded through apotentiometer I and a iixed resistancev Iii. A closed circuit is thlprovided which includes capacitance (the condenser 1) inductance (thecoil 6), and resistance (potentiometer 8 and fixed resistance It). Therise and fall of-voltage induced in the coil by the passage of anautomotive vehicle, therefore,Y charges the condenser 1, and asfthischarge leaks off through the coil and re xistance, it provides a voltagedrop across the potentiometer 8 and resistance I6. A condenser Ilcouples the variable contactar of the potentiometer with the grid II ofa ther'mlonic tube 9 so that the selected voltage across thepotentiometer 8 is applied to the grid of the tube in consequence to thedischarge of the power condenser I. Hence, with each discharge of thecondenser following the passage of a ve hicle across the detector coil apositive bias is impressed upon the grid of the tube and the tube isthus rendered conductive.

v The adjustment of the potentiometer. of course. determines theamplitude of the bias potential 11npressed upon the grid of the tubethrough the condenser H, the iixed resistance I6 serving as a minimumpoint of adjustment.

` The tube 9 may be of any suitable type and in the present instance isillustrated as a triode:

' and as is customary, a grid leak resistor i8 coacts with the condenseri I andthe cathode or diament lI2 of the tube to provide a predeterminednormal grid bias.'y

' duced in the coll is A. C..V of a frequency depend# small undesireductuetions which may be superimposed upon the impulse wave form; and inthe plate circuit of the tube 9 a condenser i3 is preferably connectedacross the c oilof the relay to filter out the ripple present whererectiiied .L C.

power supplies aroused in preference to a bat- The armature i0 of relayi5 is arranged to close a circuit 2l fed from a suitable source ofcurrent 2 and including a signal or other instrumentality web;lazctuated, designated generally by the num If the power circuit is usedto operate trame signals such as employed for highway traiiic con? trol.a timer 24 ls preferably included in the circuit to coordinate theseveral signals.

Fpr the benefit of* those skilled in the art,but not with any intentionof limiting the invention, the values for the various elements of thesystem shown in Figure 2, which is designed primarily for trame control.may be as follows:

The power condenser 1, mid.:

The inductance comprising the detector i, 88.000 turns of number 38enameled wire, having l resistance of 15,000 ohms; y

The potentiometer I, 100,000 ohms; i

The series resistance IB, 10,000 ohms;

The bypass 'condenser l1. Amid.:

The condenser Il, .5 mid.:

The grid leak Il. i0 megohms:

The A or lament voltage i3. a conventionalA storage battery of 6.3volts: The B or plate voltage. 45 volts.

The values of the power circuit 2l need not be given, and quiteobviously suitable ampiincation can be incorporated in the relaycircuitto build up the slight voltage of the initiating circuit to the valuenecessaryto operate the relay, but inasmuch as such amplication is wellknown it has not been illustrated.v

The operation of the system diagramniatically.l

illustrated in Figure 2`is as follows:

Upon the passage of a vehicle across or in proimity to the detector coil6, a. voltage is induced 'in the coil by the passage of the magneticiield' which surrounds `the vehicle. By virtue of the motionl of thevehicle past the coil. the voltage in ing upon the speed of the vehicleadwthus relatively low. but of only one cycle with the rst half of thecycle either positive or negative, de-

' .pending upon the way the coil and condenser are connected in theinitiating circuit. If condenser 1 is ofthe electrolytic variety. onlythe positive half of the A. C. impulse will be fed to the circuit. -thenegative half flowing directly to ground through the condenser. 1f apaper type condenser is used, both the positive and negative vFilzaunentvoltage is derived an adequate 4 source such as a battery i3, and theplate cir-f' i cuit of the tube, which is fed by a battery or other'source of potential; I4, contains an appropriate relay I5 to beactuated whenever the tube 9 becomes conductive, which, of course,l isdependent upon the potential of the bias on its grid IB.

To insure stability in the circuit a small car pacity condenser l1 isprovided which bypasses halves'of thecycle will flow in the initiatingcircuit. but since the negative half of the cycle will merely increasethe negative grid-bias voltage, the net result will be the same ineither case. that isythe tube will be rendered conductive during thepositive phase of the impulse cycle.

" It will be understoodthat whether the coni denser l is of theelectrolytic or paper type, it

provides'. together with the coil, a resonant circuit which, in view ofthevalu'es selected, is tuned t-o the low frequency' of the alternatingcurrents' induced in the coil by the passage of automotive vehicles inits proximity.

The potentiometer 8, which determines the amplitude of thebiaSvp-Jtential supplied by the initiating circuit, is adjusted so thatthe positive bias lplaced on the grid i0 of the tube renders the tubeconductive for a period long enough to close the relay circuit,whereupon the response of the relay armature 25 closes the powercircuit; If the service i'or'which the system is installed requiresholding the relay circuit closed for longer than parallel with thethermionic tube 9 which is conl to the 'coil is guarded against, butbeyond this no special attention need be given the installation-og thecoil.

While the circuit of Figure 2 is generally fe' ceptive to transientmagnetic fields of all types,

this is not objectionable as by proper selection of the values of `itsconstants the initiating circuit can be tuned to be responsive only tothe magnetic fields emanating from passing automotive vehicles. If theinstallation must be made in proximity to powerful sources of disturbingelecnected in a relay circuit to control the Iunctioning of a relaylB-the same as previously described.

Where cross trafilc must be controlled, the ari rangement illustrateddiagrammatically in Figure l is employed. Here it is simply a case oi'`adding the required number of detector coils and power condens'crs andconnecting all of them with a central control unit indicated generallyby the numeral 25. The "east" and west" bound traicY detectors arevconnected with this central controlby a common lead l26. The north"y'and "south" bound trailic detectors are connected with the centralcontrol by a common lead 21, Y

At the central control the impulses made b the various detectors arecoordinated and timed -to turn the "east and "west" bound signals 28 andthe north" and south bound signals 29 on and oil', a common lead 30connecting the central control with the former and a'common lead Ilconnecting the central control with the latter signals.

The requirements of the mounting for the de"- tector coil 5 are simpleas compared to those of electrical detection systems heretofore in use.

It is only necessary that the coil 5 be insulatedv from ground. but ascan be yreadily appreciated the coil should be adequately protected notonly -against the elements after installation butalso againstintentional tampering (which might occur where the coil must be mountedin an exposed location) and the rough handling which it is apt toreceive prior. during and after installation.

The most practical and feasible forni of protectivecvering is a metalsheath or casing such as illustrated at 32 inFigures 4 and 5. Spacingcollars 35 hold the coil spaced from the walls of the sheath. The sheathmay be made of any metal. but copper, brass or aluminum are preferable.l

The necessity for having the sheath or casing ungrounded is to insurethat the passage of the shown) alongside the pavement. The metal encasedcoil is then slipped lengthwise into the insulating duct 33 and. asclearly shown in Figure 4; the ends of the coil are connected tosuitable insulated conductors which pas 'through the removable cap 30 ofthe metal sheath to enter the pit (not shown) from where an undergroundcable canbe led to the central control box Obviously. the installationo! the detector coils e should-be such that the admission of moisturetrical influences, such as high tension A. C. power'lines, the simpleaddition of a condenser Il across the inductance 5, asshown in Figure 8.

will further peak or tune the initiating circuit to exclude theobjectionable induence.

If a paper type condenser is used either half of the cycle of A. C.induced in the detector coil i charges the condenser, and the initiatingcircuit takes on the characteristics of va `free oscillating circuit sothat if desired the thermionic tube may be renderedconductive a numberof times for each signal impulse, the number being deter.-

' minedY by the magnitude'o the initial charge upon condenser 1 and thesetting of potentiometer 8. Because oi' the oscillatory character of Athe responsewith a paper type condenser. the

ioutput of the detector circuit is slightly higher than in thecasewhereV an electrolytic condenser is used; however, theelectrolyticcondenser has the advantage of excluding any stray ground currents thatmight be flowing in the ground and:

is considerably more compact than a paper condenser of the requiredcapacity.

A paper type condenser is also better suited to the slightly modiedcircuit shown in Figure 6. In this circuit the voltage output is acrossthe condenser l. the -value of which may be between .5

and 2 mid.; and the potentiometer is supplantedby afixed lresistance 8of chosen value. in this vcase approximately.l5 0`,000 ohms.

" As hereinbefore indicated the core oi' the de tector coil ispreferably formed of a special alloy.

tion of magnetic impulses of extremely small magnitude. but also rapidly`passing and repeatedimpulses. Hence it is desirable that the detectorbeso designed as to make the most of these slight.

short lived impulses. `To this end the core 8 is formed of asubstantially non-retentive alloy of nickel and ronin `variousproportions to give it permeability which is high in comparison to thatof iron and steel. The proportion of nickel is 'between 40 and '75percent. the remainder being iron. .The permeability of this alloy'is inthe neighborhood o! 2,000 to 4.000, which is tive to six -tirnes thepermeability of silicon steel in the grade generally used fortransformers and magnetic type detectors. The addition of a smallamount. about 1.5% of manganese increases the permeability'to as much as10,000.

Due to the high permeability, the voltage lnduced in the coil builds uprapidly and the amplitude of the voltage is increased as a function ofthe number of. turns surrounding the core.

From the foregoing description, taken inconnection with the accompanyingdrawings. it will be readily apparent to those skilled in the art,

admirably 'adapted for use in connection with annonce' wide range oiutility.

What I claim as my invention is:

1. Detector, apparatus for detecting the pas-V detector unit and thecondenser so that dischargeof the condensereiiects a voltage drop acrossthe resistance; and means for applying a potential I' traino control. isnot limited thereto. but'ha's n derived from the voltage drop acrosstheresistl ance upon'the grid `oi' the tube to supply positive -gridbias thereto and thereby render ,the tube conductive for the passage ofcurrent by which an indicator may be actuated;

2. Apparatus for detecting the passage of vehicles and' other objectsfrom which magnetic nelds emanate, comprising: an vinduction coiladapted to have an E. M. F. inducedA therein by the passage in proximitythereto oi a vehicle or other object i'rom which a magnetic iieldemanates; a condenser adapted to be charged by the E. M. F. induced inthe induction` coil and connected between one end ofthe coil andground:a resistance connected between the other end of the'coil andl ground.said condenser, coil, and resistance forming with ground a closedcircuit so that upon the induction of an E. MI.` F. in the coil saidcondenser becomes charged, the charge on the condenser leaking. oiithrough said closed circuit and resulting in a voltage drop across theresistance: and means for impressing said voltage drop upon the grid ofthe tube to provide positive grid bias therefor and thus render the tubeconductive.

3. Detector means for use with vehicle actuated traiiic signalscomprising: an induction coil in which a voitageis induced by thepassage in proximity thereto of an vautomotive vehicle; n condenseradapted to be charged by the voltage thusinduced in the coil: meansdening a closed circuit including the coil, the condenser. and aresistance whereby the induction o! vvoltage in the coil charges thecondenser and discharge of the condenser through said circuit results ins voltage drop across the resistance; a thermionic tube adapted tocontrol a circuit for initiating the functioning of a traiiic signal:and means for impressing the voltage drop across the resistance upon thegrid of the tube so that the discharge of the condenser providespositive grid bias to render the tube conductive.

4. Apparatus for detecting the passage of vehicles and other objectsfrom which magnetic held: emanate, comprising: an induction coil adaptedto have an E. M. F. induced therein by the passage in proximity theretoof a vehicle or other object from which@ magnetic field emanates; anelectrolytic condenserv directly connected bctween one end of the coiland ground with the positive side of the condenser grounded; aresistance connected between the other end oi the coil and ground, saidcondenser, coiland resistance forming with ground a closed circuit sothat at one poiarity'the E. M. F. induced in the coil leaks oiI toground through the condenser while at the opposite polarity the E. M. F.induced in the coll places a charge upon the condenser which leaks of!through said closed circuit and in so doing eHects a, voltage dropacross the resistance; and means connecting said resistance with thegrid of the tube to impress positive bias potential upon the grid oi thetube from the voltage drop which 1 occurs across the resistance duringdischarge of "the condenser to thereby render the tube conductivc. Y

5. A detector apparatus of the character described comprising: aninduction coil adapted to 4 have an E. M. F. induced therein by thepassage in proximity thereto of an automotive vehicle: n

condenser adapted to be charged by the em! invduced in the coil; meansdening a closed circuit includingthe .coil and condenser connected inseries circuit so that a charge is built up in the condenser inconsequence to the passage of an automotive vehicle in proximity to thecoil to leak of! through the coil and said closed circuit;

. an electric current controlling device adapted to control a circuit inwhich said device is connected, said device having a control element andbeing rendered conductive by the impression upon its control element ofa predetermined small voltage; means connected with said circuit and inwhich the discharge of the condenser through the coil and said circuit.effects a voltage drop; and means for impressing said voltage drop UPOnthe control element of said current controlling device.

NICHOLAS S. RICH.

REFERENCES CITED The following references are oi' record in the iile ofthis patent:

UNITED STATES PATENTS Number Name Date 1,715,543 Elmen June 4,v 19291,751,330 Hirt Mar. 18, 1930 1,880,805 Christopher Oct. .4, 1932 l1,992,214 Katz Feb. 26. 1935 2,201,146 Barker May 21, 1940 2,243,341Horni May 27, 1941

